An elevator comprises typically a car, an elevator shaft, a machine room, lifting machinery, ropes, and a counter weight. The elevator car is positioned within a sling that supports the car. The lifting machinery comprises a sheave, a machinery brake and an electric motor for rotating the sheave. The lifting machinery moves the car in a vertical direction upwards and downwards in the vertically extending elevator shaft. The ropes connect the sling and thereby also the car via the sheave to the counter weight. The sling is further supported with gliding means on guide rails extending in the vertical direction in the shaft. The gliding means can comprise rolls rolling on the guide rails or gliding shoes gliding on the guide rails when the elevator car is mowing upwards and downwards in the elevator shaft. The guide rails are supported with fastening brackets on the side wall structures of the elevator shaft. The gliding means engaging with the guide rails keep the car in position in the horizontal plane when the car moves upwards and downwards in the elevator shaft. The counter weight is supported in a corresponding way on guide rails supported on the wall structure of the shaft. The elevator car transports people and/or goods between the landings in the building. The elevator shaft can be formed so that the wall structure is formed of solid walls or so that the wall structure is formed of an open steel structure.
The elevator shaft is provided with a pit below the lowermost landing of the shaft. In a case the depth of the pit is more than 1.6 m, two stop buttons are required for maintenance operations to be performed from the pit. The first stop button should be positioned in the shaft above the floor of the lowermost landing so that a mechanic can operate the first stop button when he is standing on the lowermost landing and the landing door is opened. The second stop button should be positioned in the pit either separately or on a maintenance drive unit positioned in the pit. Operation of the car is prevented completely when the first or the second stop button is activated as they are part of the safety circuit of the elevator.
The pit can be accessed from the lowermost landing when the car is positioned above the landing door of the first landing. The mechanic may open the lock of the landing door at a landing with a triangle key, whereby the operation mode of the elevator is changed into maintenance mode preventing normal operation of the elevator. The elevator can still be operated in maintenance mode e.g. from a maintenance access panel positioned near a landing door at a landing. Also opening of the hatch of the maintenance access panel with the triangle key will change the operation mode of the elevator into maintenance mode preventing normal operation of the elevator. After unlocking the landing door, the mechanic opens the landing door manually by force in order to be able to enter into the shaft and to climb down to the pit with a ladder. The mechanic closes the landing door manually from the shaft after entering into the shaft in order to prevent third parties and objects from falling into the pit.
The elevator car must naturally be positioned above the landing door of the lowermost landing before the mechanic can enter into the shaft in order to climb down to the pit. The mechanic may drive the elevator car in maintenance mode from the maintenance access panel to a position above the landing door of the lowermost landing if this is needed.
The procedure when entering into the pit is the following:
1. The mechanic opens the lock of the landing door at the lowermost landing with a triangular key, opens the landing door manually and activates the first stop button positioned within the shaft from the lowermost landing, enters into the shaft and closes the landing door manually from the inside of the shaft. Opening of the lock of the landing door sets the main control unit into maintenance mode preventing normal operation of the car. Activation of the first stop button opens the safety circuit of the elevator preventing operation of the car completely.
2. The mechanic climbs down along a ladder to the bottom of the pit and activates the second stop button positioned on the maintenance control unit and turns a drive switch on the maintenance control unit into a maintenance operation mode.
3. The mechanic climbs up along the ladder and deactivates the first stop button. The second stop button is still activated at this stage preventing operation of the car.
4. The mechanic climbs again down along the ladder and deactivates the second stop button. The mechanic can now drive the car with the maintenance control unit in maintenance mode downwards in the shaft to a position in which the mechanic can perform maintenance of the equipment positioned in connection with the bottom of the car.
When the mechanic has performed the intended maintenance operation he must repeat the same procedure in a reverse order.
1. The mechanic drives the car with the maintenance control unit into a position above the landing door of the lowermost landing and activates the second stop button.
2. The mechanic climbs up along the ladder and activates the first stop button.
3. The mechanic climbs down along the ladder and turns the drive switch on the maintenance control unit into an inactive operation mode and deactivates the second stop button. The first stop button is still activated at this stage preventing operation of the car.
4. The mechanic climbs up along the ladder, opens the landing door on the lowermost landing, enters into the lowermost landing, deactivates the first stop button, and locks the landing door with the triangular key.
Deactivation of the first stop button closes the safety circuit as the second stop button has been deactivated already earlier. Locking of the landing door at the lowermost landing with the triangular key will restore the elevator into normal operation mode.
This procedure is rather cumbersome as the mechanic has to climb up and down from the pit along the ladder several times. There is also a tripping risk when the mechanic has to climb several times up and down along the ladder in the shaft. There is further the risk that the mechanic will be tempted to short cut the tedious procedure. The mechanic might by mistake or deliberately forget to activate the first stop button when he enters into the shaft and climbs down the ladder to the pit.
This hazard has been prevented in prior art solutions so that the control logic of the elevator has been set to identify such a maintenance situation and to remember the situation. The control logic of the elevator identifies the start of the maintenance operation cycle when the mechanic opens the lock of the lowermost landing door with the triangle key. The control logic of the elevator remembers this maintenance operation cycle and prevents operation of the car until the maintenance operation cycle has been signed off by the mechanic at the maintenance access panel.
The singular i.e. landing door is used throughout the application, but the landing door could naturally comprise one or several door panels. The landing door could be a swing type door or a gliding type door. The swing type door and the gliding type door could comprise one or several door panels.